Data processing systems are typically built from a variety of components that are assembled into a chassis, such as one or more central processing units (CPUs), dynamic random access memory (DRAM) dual in-line memory modules (DIMMs), hard disk drives (HDDs) and other processing components. End users can tailor a data processing system's capabilities by choosing the number and types of components that are included in the data processing system. One example of this is the number of DRAM DIMMs that are included in a chassis. A server data processing system mainboard can have 48 or more DIMM sockets, each of which accepts a DIMM that stores information for ready access by a CPU. By populating the DIMM sockets with DIMMs, the end user increases the capability of the server's data processing system by increasing storage for the CPU to manage instructions and data. Additional DRAM tends to be particularly helpful with the running of complex applications and with busy data processing systems that have high CPU utilization levels. Data processing system manufacturers will sometimes include empty DIMM sockets on a mainboard so that an end user can populate the sockets with DIMMs if improved performance is desired. If all of the DIMM sockets are populated on a mainboard, then the end user is generally limited from increasing the DRAM that the CPU can access.
Data center rack space for supporting operation of a server data processing system often carries a high overhead expense. Data processing system manufacturers attempt to design the layout of a mainboard so that the data processing system includes a defined capability within a limited space. In order to maximize the processing capability within a chassis while minimizing its vertical height, manufacturers often include mezzanine cards that are positioned over and parallel to the mainboard. The mezzanine cards couple to the mainboard so that processing components on the mezzanine cards can interact with other components coupled to the mainboard. When a small-sized chassis is used to support the mainboard, the mezzanine cards can sometimes overlap other components, such as the DIMM latches, so that all of the components will fit within the chassis. These overlapping components tends to make assembly and repair of the mainboard more complex. For example, if a mezzanine card bracket couples to the mainboard with a screw or other connector and extends over DIMM sockets, then populating or replacing DIMMS in DIMM sockets might call for removal of the mezzanine card and bracket before the DIMM sockets are accessible. The access to DIMM sockets is further complicated by the minimal room typically available to access components and by grounding interfaces that provide a ground from the mainboard through the bracket to the mezzanine card.
US 2013/0223035 AI discloses a mainboard design capable of maximizing the number of expansion cards or components supported by a central processing unit on a mainboard. To achieve the above mentioned objects, the mainboard allows an expansion circuit board to be electrically connected to it. The mainboard has a primary circuit board and an adapter component. The primary circuit board has an expansion slot. The adapter component is connected to the expansion slot, and is used for being electrically connected to the expansion circuit board. The expansion circuit board and the primary circuit board are not located on the same plane.
The adapter component, which US 2013/0223035 AI discloses, has a first adapter circuit board and a second adapter circuit board. One end of the first adapter circuit board is plugged into the expansion slot, and the other end of the first adapter circuit board is connected to the second adapter circuit board in the form of one piece. The second adapter circuit board comprises a first expansion slot, wherein the first expansion slot allows installation of an expansion circuit board.